Divinity embodying endless rancour and languor (8)
I believe the answer is:
debility
'languor' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for debility that I've seen before include "Weakness (of body)" , "Weakness (from illness)" , "Feebleness, frailty" .)